Substituted benzyl nu-methylcarbamates as herbicides



United States Patent 3,399,048 SUBSTITUTED BENZYL N-METHYLCARBAMATES ASHERBICIDES Richard A. Herrett, Raleigh, N.C., and Robert V. Berthold,South Charleston, W. Va., assignors to gnifin Carbide Corporation, acorporation of New or No Drawing. Original application Apr. 2, 1963,Ser. No. 269,874. Divided and this application May 19, 1965, Ser. No.457,189

10 Claims. (Cl. 71-106) ABSTRACT OF THE DISCLOSURE Substituted benzylN-methylcarbamates, especially 3,4- dichlorobenzyl N-methylcarbamate,are used as selective pre-emergence herbicides.

This application is a division of applicants Ser. No. 269,874, filedApr. 2, 1963, now abandoned.

This invention relates to new chemical compounds useful as contactherbicides when applied to plant foliage. These compounds also displayunusual properties of selective herbicidal action when applied aspre-emergence treatments.

The undesirability of a mixed population of weed plants and crop plantsis universally acknowledged. Weeds compete for sunlight, moisture, andnutrients; they harbour insects and disease; and they create seriousproblems in the harvest operation. The .overall effect of weeds is areduction in the crop value.

Efforts to combat these weed problems have been helped considerably bythe introduction of chemicals possessing powerful hormonal properties.Generally, the chemicals will effectively remove broad-leaf weeds fromnarow-leaf or grassy crops. These chemicals are not without problems,however. Because of their toxicity to broad-leaf plants, they will killcrops not of the narrowleaf class when accidentally sprayed on suchcrops. This danger can be substantially obviated by use of a selectivepre-emergence herbicide. A second major disadvantage associated withthese materials is their failure to control grassy weeds. Thisdisadvantage has been alleviated to some extent with the introduction ofnew herbicides. Many new materials such as the triazines and substitutedareas are confronted with the problems of excessive soil residues andtheir uses are somewhat limited.

Heretofore, some of the most eflicient and widely used selectivepre-emergence herbicides were the N-aryl-O- alkyl carbamates, asexemplified by the commercially available isopropylN-(3'chlorophenyl)carbamate. These chemicals, while very useful, possessinherent disadvantages that limit their application. For example, whenapplying isopropyl N-(3-chlorophenyl)carbamate there is often found anarrow margin of safety with respect to crop tolerance to the chemical,i.e. doses only slightly higher than those required for effective weedcontrol induce undesirable phytotoxic effects in the crop. In addition,the effectiveness of this chemical is highly sensitive to soiltemperature (high activity is associated with low temperatures) and thissensitivity, coupled with the low degree of crop tolerance, frequentlymakes the use of this compound very hazardous. Another drawback to theuse 3,399,048 Patented Aug. 27, 1968 of these known carbamate herbicidesresides in their highly variable residual life in the soil, againapparently influenced by temperature.

We have now found that a new class of compounds posses the basicdesiderata of pre-emergence herbicides to a greater extent than do knownmaterials. Thus, our compounds are surprisingly superior in twofundamental respects:

(1) A high tolerance of the crop to our chemicals is is found atconcentrations sufficient for substantially complete weed control, i.e.there is a broad margin of safety to avoid undesirable phytotoxiceffects to the crop; and

(2) Broad-spectrum activity is displayed by our chemicals with respectto variety of weed species controlled and this activity is coupled withbroad-spectrum crop tolerance.

In addition, the compounds of this invention possess important secondaryadvantages in that their effectiveness is not highly susceptible tovariation with changing environmental conditions. Thus, our materialsare eifective at both low and relatively high soil temperatures, e.g.C., and their residual life appears not as adversely affected by ambienttemperature changes as that of known materials.

Our operative materials are characterized as halogenated or nitratedbenzyl N-methylcarbamates and can thus be depicted by the generalformula:

wherein X is a halogen, such as chlorine, bromine, fluorine, or iodine,preferably chlorine, or a nitro radical, and n is an integer from 1 to5.

We have found that the position of the halogen or nitro radicals on thephenyl ring has a profound influence on the herbidical activity andselective action of the compound. Thus, substitution at one or both ofthe 3 and 4 positions is vastly preferred, as demonstrated by the datain Table I, below, wherein several isomeric dichlorobenzylN-methylcarbamates were evaluated.

We have further found that other structural characteristics of our novelcompounds are narrowly critical in that even minor variation thereofresults in substantial loss of herbicidal activity. For example if thecarbamate nitrogen substitution is changed from N-methyl drasticreduction of bioactivity is observed (see Table 11, below).

In addition, it has been demonstrated that alteration of the simple CHlinkage between the phenyl ring and the oxy bridge of the ester groupresults in diminished effectiveness.

Our compounds possess activity both as pre-emergence and post-emergenceherbicides and, accordingly, one aspect of this invention comprises theapplication of the operative materials to undesired vegetation by anymeans whereby said materials are brought into contact with living plants(which include seeds and germinating seedlings), e.g., by application tothe soil before any plants emerge or by direct application to foliage.

While our materials can be applied directly to undesired vegetation andthus be used as indiscriminate plant killers, we have found surprisingselectivity when applying them to the soil in pre-emergence treatment.In such treatment both grassy weeds such as cralbgrass, wild oats,barnyard grass, yellow foxtail, green foxtail, quack grass, and ryegrass, and broad-leaf weeds such as mustard, pigweed, lambsquarters, andsheep sorrel are readily controlled while a broad spectrum of crops isunafiected. Illustrative of tolerant crops are cotton, soybeans,peanuts, beans, peas, onions, alfalfa, red clover, lespediza, fieldcorn, and the like.

In addition to soil applications, our materials are effective asalgaecides when applied to the media (e.g., water or soil) supportingthe growth of algae.

Our new toxicants may be applied conveniently in the form of a spraycontaining the active ingredient in a concentration within the range of0.0 l20.0% by weight, and preferably from 1 to 10.0% by Weight. Thoroughcoverage of the foliage is effective for contact killing. Forpie-emergence control of plants amounts within the range of A to 100pounds per acre are generally used.

Although most of the esters are insoluble in water, they are soluble incommon organic solvents. Most of them are soluble in acetone,chloroform, ethyl alcohol, ethyl acetate, benezene, ether and heptane.The esters may be dispersed directly in water or a solution in anorganic solvent emulsified in aqueous medium by the aid of a dispersingagent. As dispersing and wetting agents there may be employed soft orhard sodium or potassium soaps, alkylated aromatic sodium sulfonatessuch as sodium dodecylbenzenesulfonate, an amine salt as for exampledibutylammoniurn dodecylbenzenesulfonate, alkali metal salts of sulfatedfatty alcohols, ethylene oxide condensation products of alkyl phenols,or tall oil or higher mercaptans and other dispersing and wettingagents. Formulation of dry compositions is accomplished by mixing withfinely divided solid carriers. Suitable carriers comprise talc, clay,pyrophyllite, silica and fullers earth. Usually the toxicant will beonly a minor proportion. The dry formulation may be used as a dust ordispersed in aqueous medium before application. If the latter it isconvenient to incorporate a wetting or dispersing aid into theformulation.

Both the solid and the liquid formulations above described are useful inthe application of herbicides because they facilitate uniformdistribution and aid in the de struction of undesirable plants bymaintaining the active ingredient in a form which enables promptassimilation by the plant and efiicient utilization of its weeddestroy-- ing properties. The described conditioning agents enable theproper use [by an unskilled operator without elaborate equipment toachieve the desired herbicidal effects.

The compounds of this invention are prepared by various techniques,analogous to known methods. One synthesis involves reacting a suitablysubstituted benzyl wherein X and n are defined as before, with methylisocyanate, 'O=C=NCH to give the desired N-methylcarbamate.

The methyl isocyanate addition can be carried out, generally, bycontacting the alcohol with methyl isocyanate in an inert organicsolvent, and preferably in the presence of a tertiary amine or organotincatalyst. The reaction may be effected at temperatures ranging fromabout C. to about 100 C., and is preferably carried out between roomtemperature and about 80 C. Generally, temperatures in excess of about100 C. are to be avoided in view of the competing side reactions of theproduct carbamate. The operating pressure may range from about 1atmosphere to about atmospheres, prefer-ably from about 2 to about 3atmospheres, and is dependent upon the concentration and vapor pressureof the volatile isocyanate at the reaction temperature. The inertorganic solvents that can be employed in the reac tion are those inertto isocyanates in general, i.e. those free of radicals such as hydroxyor amino radicals. Illustrative solvents are aliphatic and aromatichydrocarbons, such as hexane, heptane, octane, benzene, toluene, and thelike, and ethers such as diethyl ether, ethyl propyl ether, and thelike. The reaction is preferably carried out in the presence of atertiary amine or an organotin catalyst or a combination thereof.Illustrative of tertiary-amines suitable as catalysts are: N,-N-dimethylhydroxyethylarnine, triethylene diamine, and dimethyl cyclohexylamine.The term organotin catalyst as used herein as meant to refer to suchcompounds as dibutyltin diacetate, dibutyltin dichloride, dibutyltindimethoxide, dibutyltin dilaurate, dibutyltin maleate, dibutyltindi-Z-ethylhexenoate, stannous octanoate, stannous oleate, and the like.Generally, amounts of said catalyst from about 0.1 to about 1.0 Weightper cent of the starting material comprised of methyl isocyanate and thebenzyl alcohol are sulficient. The mol ratio of methyl isocyanate toalcohol can range from 0.25:1 to about 4:1, but preferably an equimolaramount or slight excess of methyl isocyanate is employed to insure thatthe alcohol is completely reacted. The reaction time may vary from about5 minutes to about 7 days, but normally, when operating in the preferredtemperature range, reaction times of from about one-half hour to aboutfive hours are sufficient for complete reaction.

The carbamate product formed, either a solid or oily liquid, can berecovered from the reaction mixture by means known to the art, e:g., byvacuum-distillation to drive off solvent and excess isocyanate.

An alternative procedure involves a two-step synthesis in which thealcohol (H) is reacted with phosgene to form the correspondingchloroformate which, in turn, is reacted with methylamine to give thedesired compound as follows:

l HQN CH 0 @om-o-ii-uuom 1101 The chloroformate (III) is prepared byadding the alcohol (II) dissolved in an inert solvent, such ashydrocarbon or ether, to a solution of phosgene, dissolved in the samesolvent, at a temperature of 0 to 10 C. After allowing the reaction tocome to completion by stirring for a period of 0.5 to 4 hours, theexcess phosgene is removed under vacuum and the chloroformate strippedfree of solvent and distilled. Alternatively, the chloroformate is usedin the production of the carbamate as a residue product still containedin the reaction solvent.

The choloroformate is added to a 100 percent excess of the desired aminecontained in a solvent of the type used in the preparation of thechloroformate. The amine is used in excess to remove the hydrogenchloride evolved during the reaction which is conducted below 30 C.After allowing the reaction to come to completion, which usuallyrequires from 0.5 to 2 hours, the mixture is diluted with water, thelayers are separated and the organic layer is washed with water and thendried over a suitable desiccant such as anhydrous sodium sulfate. Thedried organic layer is distilled to remove the solvent and the resultingproduct carbamate, while usually sufficiently pure to be used as aresidue product, may be further purified by vacuum distillation orrecrystallization from a suitable solvent.

The starting alcohols (11) are compounds well-known to the art and canbe prepared by hydrolyzing the corresponding benzyl chlorides, or, canbe prepared by reducing the corresponding benzaldehyde or benzoic acidwith, e.-g., sodium borohydride or lithium aluminum hydride.

The following examples are illustrative.

EXAMPLE I 3,4-dichlorobenzyl alcohol was produced as follows: To asolution of 58 grams of 3,4-dichlorobenzaldehyde in 250 milliliters ofmethyl alcohol was added, with stirring, 9 grams of sodium borohydridein small portions and with occasional cooling to maintain the reactiontemperature below 30 C. After the addition was completed, the reactionmixture was warmed to reflux, then cooled and diluted with water. Theresulting mixture was extracted with portions of diethyl ether, theether extracts were combined and dried over sodium sulfate. The etherwas then evaporated from the combined extracts and the residual oil wasdistilled through an eight-inch column to obtain a clear oily distillateproduct, boiling point 97 C. at 0.4 mm. Hg, which solidified on cooling.The yield of 3,4-dichlorobenzyl alcohol was 92 percent of thetheoretical.

In accordance with the general procedure described above, a mixture ofgrams of 3,4-dichlorobenzyl alcohol and 20 grams of methyl isocyanate in50 milliliters of dry diethyl ether and one drop of dibutyltin diacetatewas allowed to stand in a pressure bottle at room temperature for 48hours. The ether and excess methyl isocyanate were then removed from thereaction mixture by distillation and the residual oil was distilledthrough an eightinch Vigreux column to yield 3,4-dichlorobenzylN-rnethylcarbamate as a colorless liquid distillate (boiling point 139C. at 0.5 mm. Hg) which solidified upon cooling, melting point 534 C.The yield was 83 percent of the theoretical.

Elemental analysis.Calculated for C H NO Cl C, 46.18; H, 3.87; N, 5.98;Cl, 30.29. Found: C, 46.35; H, 3.80; N, 6.10; Cl, 30.03.

EXAMPLES II-IV Using exactly the same procedure as described for the prearation of 3,4-dichlorobenzy-l N-tmethylcar-bamate (Example I),employing one drop of dibutyltin diacetate as the catalyst in all cases,the following phenyl ringsubstituted benzyl N-methylcarbamates wereprepared:

In similar fashion, the following compounds were prepared:

*Boiling point C./mm. Hg.

The effectiveness of our compounds as herbicides was determined by thefollowing tests.

Suspensions of the test compounds were prepared by dissolving one gramof compound in 50 milliliters of acetone in which had been dissolved 0.1gram (10 percent of the weight of compound) of an a'lkylphenoxypolyethoxyethanol surfactant, as an emulsifying or dispersing agent. Theresulting solution or suspension was mixed into 150 milliliters of waterto give roughly 200 milliliters of a suspension containing the compoundin finely divided form. The thus-prepared stock suspension contained 0.5percent by weight of compound. The test concentrations employed in thetests described hereinbelow were obtained by diluting the stocksuspension with water.

EXAMPLE V Compounds representative of this invention were tested withregard to pre-emergence herbicidal activity, i.e., their ability toinhibit seed germination, or to kill the seedlings at an early stage ofgrowth, by the following test.

Two seed-soil mixtures were prepared, the first by mixing 53 cubiccentimeters of perennial rye grass seed (Lolium perenne) and 27 cubiccentimeters of Florida broadleaf mustard seed (Brassica Pincea var.foliosa) with 6100 cubic centimeters of sifted, fairly dry soil, thesecond by mixing 31 cubic centimeters of Golden Millet seeds (Setariaitalica var. stramineofructa) and 12 cubic centimeters of Red Root seeds(Amaranthus retroflexus) with 6100 cubic centimeters of sifted, fairlydry soil.

Substituted Methyl Iso- Diethyl Yield Elemental Analysis Melting ExampleNumber Benzyl Alcohol Weight cyanate Ether (percent) Point,

(grams) (grams) (mllliof theory Caleu- Found 0.

liters) lated 4-ehloro-3-nitr0 12 12 35 N=11. 45 N=1l. 30 101 3-brom0 1919 40 100 N =5. 74 N =5. 68

4-bromo-3-chloro. 5 5 35 79 N =5. 03 N =5. 14 68-69 1 No catalyst used.2 Liquid product.

Each of the said two mixtures was rolled separately on a ball mill forabout one-half hour to insure uniform mixing of seed and soil, and, foreach chemical to b tested, a three-inch pot was filled with each of themixtures, and the pots removed to the greenhouse and watered lightly.

About two hours after such planting, 25 milliliters of test solutionobtained by diluting the afore-described stock suspension to 1000 partsper million with water was added to each of two pots containing the twoseparate mixtures. A control test, carried out as above but withoutaddition of test compound, was also performed. The

Thus it can be seen that of these five isomeric dichlorobenzylcompounds, the 3,4-dichlorobenzyl N-methylcarbamate is surprisinglyoutstanding in that complete kill of all four representative weedspecies was achieved. However, all of the isomers tested provided weedcontrol.

Also tested according to the above procedure were the followingcompounds pots were held in the greenhouse and watered lightly for TABLEII three weeks at which time observations were made as to Comp seed Pb tt 'i R n the extent of injury of each plant species and each test O y 0m y R e Mum Rd M t a compound was rated according to the followingdeslgna g y c R820; us ar trons.

R= 5=no seedlings emerged, or those which did emerge subsequently diedC1 4=few seedlings emerged, and many of those which did emergesubsequently died GILT 4 4 4 4 3=moderate reduction in stand 2=slightreduction in stand 01 1=no injury; seedlings appear no different withrespect to stand or growth than control 4 5 4 4 The results of thesestests are set forth in Tables I and II below. ClCHz- 4 5 5 5 TABLE I BrCompound 0 Seed Phytotoxicity Rating CH2 4 4 5 5 4]} Rye Millet RedMustard R-O- NHCH; Root Br R: CH C1 2 5 5 5 5 C1 CH, 3 3 i 5 O, ,H, 3

| C1 -CH2 4 4 4 4 C1 C1 CH- 3 4 4 3 Cl-GH; 5 5 5 a 2 2 5 3 In addition,the following compounds were tested as described above but using a testconcentration of p.p.m. c1

instead of 1000 ppm.

TABLE III Cl Seed Ph totoxlclt, Rattn v I? :1 Y 1; Cl- CO:OC-N

\ Rye Millet Red Mustard R: ROOt H H 3 3 4 3 H CH1 4 5 5 4 /CH3 H -CH 12 2 1 CH3 CH3 2 2 1 1 -C4H9 --C4He 1 1 1 l 9 EXAMPLE vi To investigatethe effectiveness of compounds representative of this invention asfoliage herbicides, i.e., in post-emergence application, the followingtests were car- 10 In most instances stunting, burning, or chlorosis ofthe treated plants were also observed. The elevated concentrations usedin obtaining these data do not preclude their utility in selectivelycontrolling weeds at lower concenried out trations. Surprisingly, riceis resistant to these compounds The test plants were snap bean(Phaseolus vulgaris var. after emergence humilis Tendergreen) with thefirst trifoliate expanding, explore W fully the pre'emergenceherblclclal field corn (Zea mays var. inducm) six inches tall, and F fof cer ta1n of our P the following Senal tomato (Lycopersicon enulentum)six inches tall. The dunno experiments were earned plants were placed ona revolving turntable and Sprayed Flat metal containers were filled withan artificial soil for thirty seconds, using a hand spray gun set at 40p.s.i.g., Consisting of sand and P moss in equal Volumes and with testcompound formulations containing 2500 parts nutrients added theretoOunces of Potassium nitrate, 4 by weight of compound per million partsof formulation. ounces of potassium sulfate, 2 /2 pounds of superphos-The sprayed plants were then removed to the greenhouse phate, 7 /2pounds dolomite lime, and 2 /2 pounds of caland held at ten Y After they Period cium carbonate lime per cubic yard of soil). These soil theresults 011 each Plant e visibly Observed and each flats were thenseeded with the indicated crops and weeds. {Ompound was rated accordmgto the followmg designa Each test compound was applied at the variousindicated trons: concentrations by pre-emergence application in whichthe 5 =plant dead 90 compound was applied to the flats within one day ofseed- 4=severe injury ing. Application was made by spraying the testformulaj y tion onto the flats moving on a continuous belt. In each l iy case the soil flats were sub-irrigated after application of mlul'y thechemical. Two weeks after application, results were A control test,carried out as above but without any test Observed and the degree ofPhytOtOXie damage rated on a compound in the formulation, resulted in noinjury to relative scale from 1 (no control) to 5 (complete kill). thecontrol plant. The results are set forth in Table V, below.

TABLE V Pro-emergence injury rating Crops Weeds Broad leaf Grass Broadleaf Grass Compound Rate 2 2 5 '0 g 3 E g E s; e a a a a g: o e 5 8 e Ea o a a a e e 5' a 5 a e 8 a? 3 a s a i 5 4-chlorobenzyl N-niethyl- {8pounds per acre. 3 1 5 2 2 4 5 4 4 4 5 5 earbamate. 2 pounds per acre-..2 1 2 1 1 2 3 2 3 2 3 3 2-chlorobenzy1 N-methyl- 8 pounds per acre-.. 21 1 1 1 1 2 3 3 2 3 3 earbamate. Benzyl N-methylcarbamate 2pounds peracre. 2 1 1 1 1 1 1 2 1 1 1 1 3,4-diehlorobenzyl N-methyl- 8 pounds peracre- 5 2 2 5 3 3 5 5 4 5 5 5 5 carbamate. {2 pounds per acre. 3 1 1 3 22 4 5 4 3 3 5 4 pound per acre.-. 2 1 1 1 1 1 3 3 2 3 2 4 33-nitro-4-ehlorobenzyl N-methyl- {8po unds per acre. 5 3 3 5 3 3 4 5 4 45 5 earbamate. 12 pounds per acre. 1 1 1 2 1 1 2 4 2 2 2 3 Table IV,below, sets forth the results of these tests. The effectiveness of3,4-dichlorobenzyl N-methylcarba- TABLE IV mate under actual fieldconditions is illustrated by the Compound following test carried outunder normal field conditions in the Southeastern United States.Phytotoxwlty Rating A field was rototilled and row-seeded with theindicated n-o-c-rvncn; Bean co Tomato crops and Weeds in October.Immediately thereafter one- R= half liter portions of a testformulation, prepared by dissolving suflicient compounds in equalvolumes of water 4 2 3 5 and acetone to give the indicated rates inpounds of compound per acre, were applied to the test plots which meas-Cl ured 3 feet by 10 feet (one plot for each plant species). 5 3 4Application of the formulation was made using a hand sprayer having asingle nozzle. Small amounts of rain 01 7 occurred twice betweenapplication and observation of results. Eighteen days after applicationof the chemical 91 4 3 3 results were observed by visual inspection andthe performance of the compound against each plant species was Br-Q-flh-4 1 3 rated according to the designations used in Example IV,

above. The results are set forth in Table VI, below.

TABLE VL-FIELD TEST EVALUATION OF 3,4-DICHLOROBENZYL N-METHYLCARBAMATEConcentration Crops Weeds (pounds per acre) Cotton Corn Mustard RyeGreen Crab- Carpet Quack Grass Foxtail grass Weed Grass In this test theplot was naturally infested, not; row-seeded, with carpet weed.

Further observation was made of the test plots during the followingspring and it was noted that the residual action of 3,4-dichlorobenzylN-rnethylcarbamate had persisted through the winter and good control ofthe carpet weed (the only winter annual of the weeds used) was beingmaintained.

Apart from the distinctive herbicidal activity of our compounds asherein disclosed, they also possess utility as insecticides, fungicides,and bactericide. In addition,

our compounds may be used to enhance or stimulate the growth of plantsby using low concentrations, or otherwise to modify plant growth.

What is claimed is:

1. A method of inhibiting undesired vegetation which comprises applyingthereto, in herbicidally effective amounts, a benzyl N-methylcarbamatewherein at least one of the 3 and 4 phenyl ring position is substitutedwith a member selected from the group consisting of halogen atoms andnitro groups.

2. The method of claim 1 wherein the N-methylcarbamate is 3-chlor0benzylN-methylcarbamate.

3. The method of claim 1 wherein the N-methylcarbamate is 3-bromobenzylN-methylcarbamate.

4. The method of claim 1 wherein the N-methylcarbamate is3,4-dichlorobenzyl N-methylcarbamate.

5. The method of claim 1 wherein the N-methylcarbamate is 4-chlorobenzylN-methylcarbamate.

6. The method of claim 1 wherein the N-methylc-arbamate is3-nitro-4-chlorobenzyl N-methylcarbamate.

7. A method of selectively controlling the growth of weeds in soil alsocontaining crop plants which comprises applying to the soil, prior toemergence of the weed plants and of the crop plants, a benzylN-methylcarbamate wherein at least one of the 3 and 4 phenyl ringpositions are halogen atoms and nitro groups, in an amount sufficient tocontrol weeds.

8. A method of selectively controlling the growth of weeds in soil alsocontaining crop plants which comprises applying to the soil, prior toemergence of the weed plants and of the crop plants, 3,4dichlorobenzylN-methylcarbamate, in an amount suflicient to control weeds.

9. A method of selectively controlling the growth of weeds in soil alsocontaining crop plants which comprises applying to the soil, prior toemergence of the weed plants and of the crop plants, 3-'brom0benzyl N-methylcarbamate, in an amount sufficient to control weeds.

10. Herbicidal compositions comprising an inert her-bicidally acceptablecarrier and, as an active toxicant, eifective amounts of3,4-dichlorobenzyl N-methylcarbamate.

References Cited UNITED STATES PATENTS 3,046,302 6/1962 Oja 7l106 3,238,036 3/1966 Herrett 7l106 2,776,197 1/1957 Gysin et a]. 71-23 3,098,0017/1963 Werres et al. 3,313,700 4/1967 Bossinger et a1. 260482 C FOREIGNPATENTS 886,425 1/ 1962 Great Britain.

LEWIS GOTTS, Primary Examiner.

G. HGLLRAH, Assistant Examiner.

